Air seeders typically include an implement frame mounted on wheels, with a plurality of furrow openers mounted on the frame. The furrow openers can be moved from a raised non-operative position to a lowered operating position where the furrow openers engage the ground and create furrows. Agricultural products such as seed and various types of fertilizer are carried in separate tanks which can be mounted on the implement frame or on a cart towed along with the implement frame.
Metering devices dispense products from the tanks into one or more air streams that carry the products through a network of hoses and manifolds to the furrow openers where same are deposited in the furrows. Although it is still common to meter two separate products, such as seed and a fertilizer, into a single air stream for delivery to a single furrow, most modern air seeders also have distribution networks that deliver one product or combination of products into one furrow and another product or combination thereof into a different furrow. For example seed is delivered to seed furrows and fertilizer to separate fertilizer furrows.
These may be comprise separate furrow openers mounted on separate shanks, such as mid row fertilizer banding furrow openers which are remote from the seed furrow openers, or combination furrow opener where a single shank supports a furrow opening tool that makes one furrow for seed and a separate furrow for fertilizer. There are also then two separate distribution networks, one delivering product from selected ones of the tanks to the seed furrows, and one delivering product from selected ones of the tanks to the fertilizer furrows.
In one typical type of air seeder a metering roller, auger, or the like dispenses product from each tank into an air stream. To accomplish this the tanks must be sealed and pressurized and a conduit generally connects the air stream to the top of the interior of the tank to pressurize the tank so that there is no pressure differential between the tank and the air stream which would put back pressure on the product as it is being metered into the air stream.
In a second type of air seeder, the tanks are not sealed and pressurized, but instead the product is metered into a venturi system such as disclosed for example in U.S. Pat. No. 6,230,636 to Bom et al.
Valmar Airflo of Elie, Manitoba, Canada manufactures implements for metering granular products from a tank through a venture into an air stream.